Ballasts for powering two fluorescent lamps simultaneously start the lamps when power is received from a power supply such as a household power switch (i.e., 120V AC). Starting the ballast includes checking for fault conditions and, upon finding no faults, driving a switching operation of an inverter of the ballast to provide power to the lamps via a resonant circuit of the ballast. When a lamp is disconnected from the ballast or a fault occurs with one of the lamps (e.g., a filament breaks or becomes nonconductive), the ballast prevents the inverter from performing the switching operation. That is, the inverter is shut down. The inverter remains shut down until the power to the ballast from the power supply is disconnected and subsequently reconnected, or until a monitored filament of the two lamps is disconnected from the ballast and subsequently reconnected, causing a restart (i.e., relamping) of the ballast. For example, if a user removes and replaces the lamp having the monitored filament, the ballast automatically restarts when the lamp is reconnected to the ballast (e.g., reinserted into a fixture containing the ballast). If the user instead removes and replaces the other lamp, not having the monitored filament, the ballast shuts off when the lamp is removed, and remains off even after the lamp is reconnected to the ballast. The user must remove and replace the lamp having the monitored filament, or cycle the power to the ballast (i.e., turn the power to the ballast off and back on) in order to restart the ballast.